Method of and apparatus for treating emulsions with alternating current



METHOD OF AND APPARATUS FOR TREATING EMULSIONS WITH ALTERNATING CURRENT Filed July 19, 1927 t through the treating space. The electric field Patented Dec. 29, 1931 UNITED s'ra'ras PATENT OFFICE CHARLES W. GIRVIN, OI LONG BEACH, CALIFORNIA, ASSIGNOR TO'PETROLEUM RECTI- FYING COMPANY OF CALIFORNIA, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA METHOD OI AND APPARATUS FOR Application filed July 19,

My invention relates to the art of treatin emulsions for separating the phases thereo and more particularly to electric methods and apparatus used in that art.

.I In the usual apparatus for electrically treating emulsions, a treating space is formed between live and groundedelectrodes and an electric field is set up between the electrodes and an emulsion to be treated is then passed set up in the treating space tends to agglomerate the particles of liquid comprising the dispersed phase of the emulsion so that at the conclusion of the treatment, these particles have all been agglomerated into large drops which easily separate out of the continuous phase of the emulsion by gravity. Both direct and alternating currents have been used in setting up this electric field, but alternating current has been found far superior to direct current because of its di-directional character. 1

, In my investigations of the treating action of electric current on many different emulsions, I have discovered that some kinds of emulsions are best treated by constant vo1tages per unit-distance of electrode spacing, while others are best treated by rapid variations in voltage per unit-distance. This constant voltage gradient could be easily secured by using direct current, and the rapid variation. in voltage gradient by using direct current with an interrupter; but direct current has never been entirely satisfactory and interrupters are inefiicient'when used with high voltages. Furthermore, high direct current voltages are often difficult (if attainment.

I have found it possible to produce substantially constant voltage gradients between a pair of electrodes when an alternating potential is impressed thereacross, by relatively moving the electrodes in synchronism with the variations of the alternating potential. By proper design, it is possible to secure a substantially constant gradient between a pair of electrodes, the word gradient in this application being defined as the quotient of volts divided by distance, disregarding the algebraic sign of voltage at any instant.

It is an object of this invention to provide TREATING EMULSIONS wrrn ALTERNATING CURRENT 1927. Serial No. 206,828.

a novel method of producing a substantially constant gradient between a pair of electrodes when an alternating potential is impressed across these electrodes.

Another object of this invention is toprovide a combination of a pair of electrodes, one of which is moved in synchronism with an alternating potential impressed across these electrodes.

A further obj ect of this invention is to provide a pair of electrodes, and a means for moving one of these electrodes relative to the other in such a manner that the distance therebetween is a function of an alternating potential impressed across these electrodes.

It is another object of my invention to provide a method of and apparatus in which an alternating voltage is used in conjunction with relatively movable electrodes, so that either a constant voltage gradient or a very rapid variation in voltage gradient may be obtained.

It is a further object of this invention to provide a method of and apparatus for electrically treating emulsions'to separate the phases thereof, in which a field is set up be tween a pair of electrodes by means of an alternating potential, this field having a gradient which is substantially constant during substantially the whole length of any given half-cycle.

While my invention may be used in the treatment of many diiferent kinds of emulsions, it is particularly adapted for, and will be described in connection with its use in the dehydration of water in oil emulsions.

Further objects and advantages will be manifest in the following description and the accompanying drawings in which a preof the alternating current used in the treater of my invention.

Referring specifically to the drawings:

The treater shown in Fig. 1 is indicated generally by the number 10, and includes a tubular shell 11 having a tight cover plate 12 and a tight bottom plate 13, which co-operate with the shell 11 to form an emulsion treating chamber 14. I

Disposed centrally in the lower portion of the chamber 14 for the purpose of introducin an emulsion thereinto is a circular manifol 15 which is supplied with emulsion by a pipe 16 extending inwardly through the shell 11. A water outlet pipe 17 connects with the shell 11 so as to drain water from the lower portion of the chamber 14 when desired. In order to conduct oil from the upper end of the chamber 14, an oil outlet pipe 20 is provided in the cover plate 12.

- Disposed within the chamber 14, a slight distance above the manifold 15, is a grounded electrode 22, which comprises a plate bent into a wavy form and having portions 23 of maximum radius and portions 24 of a minimum radius relative to the center of the chamber 14. The electrode 22 is supported by brackets 26 provided on the inner surface of the shell 11.

The cover plate 12 has a central opening 30 therein and an anti-friction bearing 31 is formed above the opening 30 so as to support an insulator 32 having a ring gear 33 incorporated therewith. Meshing with the ring gear 33 is a pinion 34 which is mounted on a shaft 35 j ournaled in a bracket 36, provided on the cover 12, for the purpose of rotating the ring gear 33 and the insulator 32 at a predetermined speed.

Fixed centrally within the insulator 32 is an electrode supporting rod 40 which extends downwardly co-axially with the treating chamber 14, and supports a rotating electrode 41 at its lower end. The electrode 41 is disposed within the electrode 22, as clearly shown in the drawings, and includes a hub 42 having a number of equal arms 43 radiating from the hub 42, these arms 43 being equal in number to the portions 23 of maximum radius of the electrode 22. Each of the arms 43 has a plate 44 provided u 11 its outer extremity. The arms 43 are of equal length so that when the rotating electrode 41 is rotated, each of the plates 44 is successively brought into the same relation with the various portions 23 and 24 of maximum and minimum radius. Owing to the maximum and minimum portions of the electrode 22 being formed in the same number respectively as the number of arms 43, the arms 43 at all times bear the same relation to the corresponding portions of the electrode 22 opposite which these arms are disposed.

The upper end of the electrode supporting rod-40 extends a slight distance above the insulator 32 and a contact ring 46 is formed thereon and is contacted by a brush 47 connected by a conductor 48 to one terminal of a secondary 49 of a transformer 50. The opposite terminal of the secondary 49 is grounded by the conductor 51 to the shell 11 which in turn is grounded to the earth by a conductor 52. The transformer 50 is adapted to supply to the electrodes an alternating potential of a wave form illustrated in Fig. 4. In this figure I have illustrated a sinusoidal wave 54 plotted on a zero axis 55. One cycle of the alternating potential is represented by that portion of the curve between points 56 and 57 this portion being in turn made up of positive and negative half-cycles 58 and 59 having positive and negative peaks 60 and 61 thereon.

It is, however not necessary that a potential of sinusoidal wave form be utilized. Wave potentials of other forms may be utilized, provided the electrodes are suitably formed so that the voltage therebetween at any given instant is proportional to the separation of these electrodes at this instant.

The operation of my invention is as follows:

Before treatment of an emulsion may be commenced, the chamber 14 is filled with a suitable dielectric liquid, preferably a dry oil of the same character as that contained in the emulsion to be treated; The transformer 50 is now energized from a source of alternating potential which may be 50 or 60 cycle current if desired. or may be of a higher or lower number of cycles. The shaft 35 is connected to suitable mechanism (not shown) that is operated by the same source of potential which energizes the transformer 50 in such a manner that the electrode 41 is rotated in synchronism with the cycles of the potential. The speed of this rotation is such that electrode 41 is positioned as shown in Fig. 2 during each positive and negative peak of voltage and is positioned, as shown in Fig. 3, at each instant that the voltage drops to zero.

When the rotation of the electrode 41 has been so regulated as to be in perfect synchronism with the cycles of the source of alternating potential, as above described, the emulsion is introduced through the manifold 15 so as to flow upwardly through the electrode 22.

As previously stated, it is an object of the invention to secure a treatment of this emulsion by a constant voltage gradient between the electrodes 22 and 41. This is accomplished by the synchronous movement of the electrode 41 relative to the various portions of maximum and minimum radius of the electrode 22. These portions of electrode 22 are so formed that the distance between each of the plates 44 and an adjacent portion of the electrode 22 is always in direct proportion to the actual instantaneous voltage of the current. Thus, when the voltage is at its positive peak 60, as shown in Fig. 4, or at negative peak 61, the electrode 41 is positioned, as shown in Fig. 2, so that each of the plates 44 is at its maximum distance from the adjacent portion of the electrode 22. Moreover,

as the voltage of the current decreases from the peaks 60 and 61 to zero, the plates 44, by virtue of the rotation of the electrode 41, move from the position in which they are shown in Fig. 2 to the position to which they are shown in Fig. 3, where they are disposed at a minimum distance from the electrode Theoretically, the plates 44 would touch the electrode 22 at the points of minimum separation of the plates 44 and the electrode 22 but as this is impracticable in the operation of the treater, the electrode 22 is so formed that a slight space intervenes between the electrode 22 and the plates 44 at the minimum distance of separation.

For such emulsions as may better be treated with a very rapid variation in voltage gradient, the center rotating electrode (or the stationary electrode) may be shifted ninety electrical degrees in which case the peaks of the voltage wave would occur at the instants of minimum electrode distance between electrodes, and it will be seen that this will result in a very great variation in voltage gradient as the electrode 41 turns.

It is desired to point out that, while in the apparatus shown, a central live electrode is rotated relative to the outer grounded electrode, nevertheless, this arrangement is merely shown as apreferred embodiment and either of the electrodes might be grounded as long as the other electrode is alive, and also either or both of the electrodes might be rotated to secure the synchronous relation described.

The use of the term constant voltage gradient in this description and in the appended claims should be interpreted in the light of the disclosure. This term is used to define the voltage per unit-distance at any instant of time, and, as previously mentioned, disregards the algebraic sign of the voltage used at this instant. Thus, whether the voltage impressed is at a positive or negative peak does not affect the gradient as this term has been used. When necessary to distinguish the gradient produced on the positive half-' cycle and the negative half-cycle, I have designated the former as a gradient in one direction and the latter as a gradient in another direction.

I claim as my invention:

1. A method of treating emulsions elecvoltage gradient, and passingan emulsion through said treating space.

2. A method of producing an electric field of substantially constant voltage gradient which comprises: moving one of a pair of electrodes relative to the other and in synchronism with an alternating potential impressed across said electrodes so that the distance between said electrodes at any instant is substantially directly proportional tothe instantaneous potential impressed across said electrodes at this instant.

3. A method of producing an electric field of substantially constant voltage gradient which comprises: moving one of a pair of electrodes relative to the other and in synchronism with an alternating potential impressed across said electrodes so that the voltage gradient in'the space between said electrodes is substantially constant over a substantial portion of each half-cycle of said alternating potential.

4. In combination: a primary electrode of wave form; a secondary electrode providing an arm extending adjacent said primary electrode; and means for moving one of said electrodes relative to the other in synchronism with an alternating potential impressed across said electrodes, said electrodes being formed in a manner that the distance between said arm and said primary electrode at a given instant is a function of the value of the voltage impressed across said electrodes at this instant.

5. In combination: a primary electrode of wave form; a secondary electrode providing an arm extending adjacent said primary elec-v trode; and means for moving one of said electrodes relative to the other in snychronism with an alternating potential impressed across said electrodes, said electrodes being formed in a manner that the distance between ing potential impressed across said electrodes.

7. In combination: a primary electrode of wave form; a secondary electrode providing an arm extending adjacent said primary electrode; and means for rotating oneof said electrodes relative to the other in synchronism with an alternating potential impressed across said electrodes,-said electrodes being formed in a manner that the distance between said arm and said primary electrode at a given instant is a function of the value of the voltage impressed across said electrodes at this instant.

8. In combination: a primary electrode; a

secondary electrode; and means for relatively rotating said electrodes so that the distance therebetween changes synchronously with the cycles of an alternating potential 5 impressed across said electrodes.

9. In combination: a primary electrode; a a secondary electrode; means for impressing an alternating potential across said electrodes, each cycle of said alternating potential com 7 1o prising two half-cycles; and means synchronized with the frequency of said alternating potential for moving one of said electrodes relative to the other in such a manner that the voltage gradient between said electrodes is substantially constant over substantially the whole length of a half-cycle.

10. In combination: a palr of electrodes; and means for relatively moving said electrodes in synchronism with an alternating potential impressed across said electrodes.

11. A process of agglomerating the dispersed particles of an emulsion, which includes the steps of: subjecting said emulsion to a voltage gradient of substantially constant magnitude for a short period of time; and substantially instantaneously reversing said gradient and maintaining it constant for another short period of time, whereby the equilibrium of said dispersed particles of said emulsion is disrupted by the quick change in direction of voltage gradient.

12. A process of agglomerating the dispersed particles of an emulsion, which includes the steps of: passing said emulsion between a pair of electrodes energized by an alternating potential comprising positive and negative half-cycles; and changing the spacing of said electrodes to create a very quick change in direction of voltage gradient at an ac instant between said positive and negative half-cycles.

13. A process of agglomerating the dispersed particles of an emulsion, which includes the steps of: passing said emulsion be- 46 tween a pair of electrodes energized by an alternating potential comprising positive and negative half-cycles; and changing the spacing of said electrodes to create a voltage gradient of substantially constant value dur- 60 ing said positive half-cycle and a voltage gradient of opposite direction and substantially constant value duringjsaid negative half-cycle, the change in direction of said gradient occurring between said half-cycles and taking place practically instantaneously in a manner to disrupt the equilibrium of said dispersed particles.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 14th day of July, 1927.

CHARLES lV. GIRVIN. 

